Currently, many of the chemicals in common use are derived from petroleum feedstocks. However, petroleum is present in limited underground reserves, and the extraction, transportation, and refining of petroleum can have severe environmental consequences.
Bio-based feedstocks, on the other hand, can be obtained from plants and can be processed by biological processes such as fermentation. To more fully utilize bio-based materials, it is often necessary to convert the fermentation products or other bio-based feedstocks into other chemicals that can be used in a variety of processes and products. Thus, it is an object of the present invention to provide new methods of converting sugars, sugar alcohols and other small molecules into a variety of desired chemical products.
For a long time, scientists and engineers have sought to convert sugars and sugar alcohols into other chemical products. For example, Conradin et al. in U.S. Pat. No. 2,852,270 (filed in 1957) reported that for increased production of propylene glycol, hydrogenolysis should be conducted over a Ni/Cu catalyst on a carrier such as magnesium oxide.
In U.S. Pat. No. 3,030,429 (filed in 1959), Conradin et al. stated that hydrogen splitting of saccharose to glycerol and glycols can be carried out in the presence of practically any technically feasible catalyst, provided that sufficient alkali is added to ensure a pH of 11 to 12.5. In one example, it was reported that hydrogenolysis of an aqueous saccharose solution over a nickel-on-kieselguhr catalyst proceeded with an 83% conversion to a product containing 43% glycerol and 25% propylene glycol.
Sirkar in U.S. Pat. No. 4,338,472 (filed in 1981) reported sorbitol hydrogenolysis to produce glycerol over a nickel-on-kieselguhr catalyst in which an alkali promoter was added to the feedstream to control pH and prevent leaching of nickel from the catalyst.
Tanikella in U.S. Pat. No. 4,404,411 (filed in 1983) described the hydrolysis of sorbitol and xylitol in nonaqueous solvents containing at least 10 mole % base. The catalyst used in the examples was nickel on silica/alumina. Distribution of ethylene glycol, propylene glycol and glycerol were reported.
Gubitosa et al. in U.S. Pat. No. 5,600,028 (filed in 1995) discussed the hydrogenolysis of polyhydric alcohols, such as sorbitol, over a ruthenium-on-carbon catalyst. In the examples, Gubitosa et al. reported that 100% of the sorbitol can be converted, with 41 to 51% of the product carbon atoms in propylene glycol.
Despite these and other efforts, there remains a need for new methods of converting sugars and sugar alcohols to smaller molecules that have a variety of uses. There is also a need for novel methods of converting molecules such as xylitol and lactic acid into higher value products such as propylene glycol and 1,3-propanediol. There is especially a need for new methods of such conversions that provide better yield and more desirable product distributions.